An UMTS (Universal Mobile Telecommunication System) network includes a core network of various elements and also a radio access network, called UTRAN (UMTS terrestrial radio access network). A UTRAN includes radio network controllers (RNCs) that control so-called Node Bs, that in turn wirelessly communicate with UE (user equipment) devices, i.e. e.g. mobile phones. UMTS networks are provided and operated as specified by 3GPP (Third Generation Partnership Program) specifications, which are evolving, and which are issued in successive releases.
In the most current evolution, which will issue as release 6, a proposal has been made for a fast Node B controlled scheduling mechanism requiring both the UE and the Node B to individually maintain a data rate pointer for the UE maximum allowed UL (uplink) data rate, as indicated in a transport format combination indicator (TFCI) data object. The data rate pointer is updated using differential signalling (increase/decrease), and so if the UE and the Node B do not have the same understanding of the current pointer value, a Node B command (a granted request or a command without a corresponding request) to increase or decrease the data rate will result in a data rate different than expected by the Node B. According to the proposal, a UE can only request a change of the data rate pointer (using rate request signalling), and the Node B is in control; if it finds a rate request from a UE acceptable, it updates its own pointer entity and signals a rate grant to the UE. Now, if the UE receives a rate grant message erroneously, the UE data rate pointer and the Node B data rate pointer become misaligned. (Additionally, as indicated above, the Node B can also command the UE to decrease its data rate pointer without the UE making a corresponding request, and misalignment can occur in that scenario as well.)
What is needed is a mechanism to ensure that misalignment of the UE and Node B data rate pointers does not occur, or, if it does, that the misalignment is corrected.